The Captain and The Doctor in “Twice Upon a Time”

[as he takes in the TARDIS interior] Is this madness? Am I going mad?

Madness? Well, you're an officer from World War One at the South Pole being pursued by an alien through frozen time. Madness was never this good.

World War One?

Judging by the uniform, yes.

Yes, but what do you mean... "One"?

[realizing] Oh, sorry. Spoilers.